Quantifying runoff variability and Glacier thickness variations from 2011 to 2020 in Gangotri glaciated region, India

Recent research indicates a substantial reduction in glacier mass within the Himalayas, primarily attributed to rising temperatures, leading to heightened uncertainties regarding downstream water availability. This study specifically investigates the impact of variations in thickness within the Gangotri glaciers, focusing on the Raktavaran and Chaturangi regions, during the period from 2011 to 2020. Employing a two-model coupling approach, the study integrates Glacier Bed Topology (GlabTop2) and Spatial Process in Hydrology (SPHY). Calibration is meticulously carried out through a two-step process, incorporating observed discharge data and Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover information. The achieved R2 values for SPHY-modeled runoff (Q) and observed Q at Bhojwasa exhibit a commendable level of comparability, standing at approximately 0.73 on a daily scale. The analysis highlights that glacier-derived Q contributes to 22.11% of the total Q, with snow-derived Q accounting for 66.91%, underscoring their distinct roles in the hydrological system. A comparative assessment between Chaturangi and Raktavaran with the Gangotri glaciers reveals that the latter experienced a more substantial rate of thickness change, resulting in an estimated reduction of about 9.40% in mean glacier thickness over the period from 2011 to 2020. In consideration of these findings, the study emphasizes the urgent necessity for a comprehensive understanding of the intricate interplay between glacier dynamics and hydrological processes within the context of changing climatic conditions. This research contributes valuable insights that can serve to inform adaptive strategies and resource management practices aimed at addressing the evolving challenges posed by glacier melt and its downstream implications.